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Effect of isolated roughness element height on high-speed laminar–turbulent transition

  • David Estruch-Samper (a1), Richard Hillier (a2), Leon Vanstone (a3) and Bharathram Ganapathisubramani (a4)


Understanding of the roughness-induced laminar–turbulent transition of supersonic and hypersonic flows is partly challenged by the intricate sensitivities presented by different correlation criteria. We investigate experimentally the effect of height for an isolated roughness element of quadrilateral planform. Heat transfer measurements document the enhancement of roughness-induced disturbances – here the associated heat flux perturbation – along a downstream axisymmetric laminar separation. With increasing element height $k$ , a gradual intensification in wake disturbance levels is found for subcritical elements ( $k/\unicode[STIX]{x1D6FF}_{k}<0.15$ , where $\unicode[STIX]{x1D6FF}_{k}$ is the undisturbed boundary layer thickness) while elements taller than the effective condition ( $k/\unicode[STIX]{x1D6FF}_{k}\geqslant 0.32$ ) bypass the more moderate transition mechanisms to produce a fully turbulent element wake. Results exhibit high sensitivity to flow properties at roughness height between critical and effective conditions. A reduction in wake disturbance levels with increasing height is documented within $0.23\leqslant k/\unicode[STIX]{x1D6FF}_{k}\leqslant 0.32$ . This effect coincides with a decrease in kinematic viscosity at roughness height $\unicode[STIX]{x1D708}_{k}$ (as Mach number at height $M_{k}$ increases from 1.52 to 1.96) and is restricted to elements with strong local separation, whereby the influence of local shear effects is enhanced.


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Bernardini, M., Pirozzoli, S. & Orlandi, P. 2012 Compressibility effects on roughness-induced boundary layer transition. Intl J. Heat Fluid Flow 35, 4551.
Berry, S. A. & Horvath, T. J. 2008 Discrete roughness transition for hypersonic flight vehicles. J. Spacecr. Rockets 45 (2), 216227.
Choudhari, M., LI, F., Chang, C.-L. & Edwards, J.2009 On the effects of surface roughness on boundary-layer transition. NASA Rep. LF99-8476.
Choudhari, M., Li, F., Chang, C.-L., Norris, A. & Edwards, J.2013 Wake instabilities behind discrete roughness elements in high speed boundary layers. AIAA Paper 2013-0081.
Choudhari, M., Li, F., Wu, M., Chang, C.-L., Edwards, J., Kegerise, M. & King, R.2010 Laminar-turbulent transition behind discrete roughness elements in a high-speed boundary layer. AIAA Paper 2010-1575.
De Tullio, N., Paredes, P., Sandham, N. D. & Theofilis, V. 2013 Laminar-turbulent transition induced by a discrete roughness element in a supersonic boundary layer. J. Fluid Mech. 735, 613646.
De Tullio, N. & Sandham, N. D. 2015 Influence of boundary-layer disturbances on instability of a roughness wake in a high-speed boundary layer. J. Fluid Mech. 763, 136165.
Estruch-Samper, D. 2016 Reattachment heating upstream of short compression ramps in hypersonic flow. Exp. Fluids 57 (5), 117.
Fedorov, A. 2011 Transition and stability of high-speed boundary-layers. Annu. Rev. Fluid Mech. 44, 7995.
Fiala, A., Hillier, R. & Estruch-Samper, D. 2014 Roughness-induced turbulent wedges in a hypersonic blunt-body boundary layer. J. Fluid Mech. 754, 208231.
Fiala, A., Hillier, R., Mallinson, S. G. & Wijensinghe, H. S. 2006 Heat transfer measurement of turbulent spots in a hypersonic blunt-body boundary layer. J. Fluid Mech. 555, 81111.
Horvath, T. J., Zalameda, J. N., Wood, W. A., Berry, S. A., Schwartz, R. J., Dantowitz, R. F., Spisz, T. S. & Taylor, J. C.2012 Global infrared observations of roughness induced transition on the Space Shuttle Orbiter. NATO RTO-MP-ABT-200, Art. 27.
Iyer, P. S. & Mahesh, K. 2013 High-speed boundary-layer transition induced by a discrete roughness element. J. Fluid Mech. 729, 524562.
Kegerise, M., King, R., Owens, L., Choudhari, M., Norris, A., Li, F. & Chang, C.-L.2012 An experimental and numerical study of roughness-induced instabilities in a Mach 3.5 boundary layer. NASA Rep. 2012-0007198.
Reda, D. C. 2002 Review and synthesis of roughness-dominated transition correlations for reentry applications. J. Spacecr. Rockets 39 (2), 161167.
Reshotko, E. 2007 Is Re 𝜃/M e a meaningful transition criterion? AIAA J. 45 (7), 14411443.
Reshotko, E. & Tumin, A. 2004 Role of transient growth in roughness-induced transition. AIAA J. 42 (4), 766770.
Schneider, S. P. 2008 Effects of roughness on hypersonic boundary-layer transition. J. Spacecr. Rockets 45 (2), 193209.
Subbareddy, P., Bartkowicz, M. & Candler, G. 2014 Direct numerical simulation of high-speed transition due to an isolated roughness element. J. Fluid Mech. 748, 848878.
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